I have completed the course. Regarding SSL, I only knew about determining whether a certificate is trustworthy by Googling the public key of the CA installed on the PC, but I have a chance to properly learn about the organizations related to certificates, such as symmetric key ~ asymmetric key ~ hybrid method ~ PKI authentication system flow. Thank you. --------------------------------------- For your information, the tuition fee of 44,000 won for this course is not expensive for students compared to the class time. For those who are taking the course, I recommend subscribing to the instructor's YouTube channel and visiting the community, where the instructor gives out coupons for his lectures every month, and using the coupons to receive a discount and take the course.